Fuel tank sender vapours in boot

[dc7531]

I have searched some of the older threads but could not find anything specific on an issue I am having with fuel vapours in the boot.

Fuel seems to weeping up through the screws and surrounds of the fuel tank sender unit filling the boot with vapour (I have to leave the boot lid ajar when stored) I first noticed it about a year ago and applied gasoline resistant 'permatex' sealant in and around the unit which seemed to stop it for a while. It is now worse than ever and just wondering if anybody has come accross this before or can suggest a more permanent fix.

Derek

[Modena]

Is your breather hose/system working properly and not gunked up?

[dc7531]

Modena, the hoses are all less than three years old, I have followed most of them except for the one to the charcoal cannister and all seem ok (no kinks etc) I will check out closely asap. The cannister (tucked in above the suspension) may be older so may need a check, if any inlets or outlets are blocked, could this be the source of any back pressure in the tank???

The fuel is appearing around the sender unit surrounds so after research on the internet (seems to be a common problem), am also considering cleaning up the sender unit area, replacing the gasket and using some Hylomar gasket sealer (especially on the threads) to see if that will help.

Derek

[Rick Parker]

Does the sending unit have 5 or 6 10-32 screws around the perimeter securing it to the body of the tank? If so it should have a neoprene rubber gasket sealing the sending unit to the tank. Sealing the threads is a good idea.

[Rog246]

The stuff to use to seal around your tank fixtures is STAGG Jointing Compound.
Its been around since Jesus played fullback for Jerusalem ! Its brown and seals perfectly as is not petrol resistant..............its petrol proof & stuff its used on stays stuck almost permanently, so use wisely.
Rog

[Modena]

Sounds like nasty (good) stuff Rog, I wouldn't want to get it on me!

[dc7531]

Rick, the sender unit has 6 screws and from memory, has a cork gasket.

Rog, I'll check out the Stagg compound asap, sounds like it will do the job.

Thanks Derek

[Merv and Sharon]

Is the hose an impermeable one? There was an earlier thread on that.

[mickmate]

When I leak test tanks they will leak up and around the sender screws so I use a sealing washer under the screw heads as a little gasket for each one. We have ethanol in the fuel here which eats a lot of bladders, gaskets etc. Use the best gasket and sealer you can.

[dc7531]

Merv, yes I remember reading the previous thread about vapour leaking through certain hoses but as Warwick supplied the new hoses and the weeping is just around the top of the sender unit, I feel the hoses are fine. When I first applied the gasket goo around the sender, the weeping stopped for several months but is now back (I think the fuel has broken down the Permatex) I finished work too late today to purchase some Hylomar, Stag compound, new gasket and now washers (thanks Mickmate) but will do so asap and see how it goes.

[Zedn]

Anyone got a source for some fuel safe rubber sheet to make gaskets out of? I need about 200mm square.

Im glad i saw this about the Permatex as i literally have a tube sitting there about to use on the pump cover. I guess the problem is that when the tank is full up to the top of the filler there is a head of fuel attempting to flood its way out.

[Aussie Mike]

Use some small fiber washers under the heads of the retaining screws. Cork gaskets can dry out as well. You could try making a neoprene rubber gasket. Neoprene is fuel proof, it's what a ot of the rubber parts in fuel systems are made from. You can buy sheet neoprene from Clark rubber in different thickneses and cut it out with scissors and a sharp knife. Use a wad punch for the bolt holes.

Cheers

[Modena]

The sender I am using (VDO) came with fiber washers for the bolts, cork gasket for the top of the flange and some sort of rubber-type gasket for the inside-tank-side of the flange.

[mickmate]

I use EPDM roofing rubber for gaskets, check with your local builder mates or supplier. While we're on roofing products what about the washers off roofing nails for the screws. I use nylon washers under my screws.

[hp1050]

We had the same problem with our Harrison, the problem was that the proper surround that held the fuel pump down which is metal was not fitted. Once it was fitted the issue was resolved. If you have this then sica flex is good as long as plan on never removing it!

[dc7531]

Originally Posted by Modena

The sender I am using (VDO) came with fiber washers for the bolts, cork gasket for the top of the flange and some sort of rubber-type gasket for the inside-tank-side of the flange.

Modena, my sender is also VDO, I remember the fibre washers and cork gasket but can't recall seeing that rubber gasket you mentioned (it has been several months since I last took the sender out though and my memory is not the best) I wont be home until the weekend but will clean up and check that all the bits are there asap.

Derek

[Modena]

there is of course two flanges, one notched that goes inside the tank, and one for the top of the tank, the notched one inside should have a gasket too.

[dc7531]

Originally Posted by Modena

there is of course two flanges, one notched that goes inside the tank, and one for the top of the tank, the notched one inside should have a gasket too.

I had a chance today to clean up and remove the sender and found nothing out of the ordinary according to this VDO diagram I found on the web. The sender had 1 neoprene gasket between the top sender flange and the top of the tank (nothing on the underside between the tank and the bottom flange) along with small red fibre washers and spring washers for the 6 screws. I will replace all of the gaskets but will also try adding another neoprene gasket above the bottom flange as suggested above. Hopefully, with some carefully placed Hylomar and Stag, the problem will be fixed. Any further suggestions?

Derek

[dc7531]

Just an update on the vapour problem. I added a neoprene gasket to the underside of the flange and with the screws coated in Permatex, the fuel does not weep anymore through the sender. Fumes may have also been exiting through a faulty connector on the fuel return hose at the fuel pump but this has also been replaced. So all good, test runs are now fume free. Thanks for all the assistance from the forum and to Craig (raaps) for the time at the workshop. Next job is to get cool air into the air filter as hot air from the fan is affecting the sensor at the air intake - lots of great ideas from recent postings but I'll probably keep it basic.

Derek

[Barker]

Stag fixed my issues with the same problem